Severe malnutrition in early childhood has been shown related to later developmental disability, but there are few prospective population studies on the sequellae of the more marginal malnutrition that commonly occurs in interaction with malaria and other infections in developing countries. During 1968-69, I obtained detailed growth, illness, and sociodemographic data on such a total cohort of pre-school age children in ten remote villages in Ulu Trengganu, Malaysia. I propose to follow-up on them now to assess their developmental status at ages 10-14. My principal objectives and operational hypotheses are as follows: 1. Assessment of physical sequellae: Poor growth in 1968-69 will predict interval mortality and poorer nutritional status now. Heights will be closer to international norms now than then, with varying degrees of "catch-up" growth predicted by prior measurements. 2. Assessment of mental development: Heights in 1968-69 will predict present scores on tests of cognitive skills better than present heights, but both associations will persist when the effect of parents' heights is controlled for. 3. Assessment of social influences on development: Stability and pattern of family constellations and economic status will predict both height and cognitive skills, but an association of height and cognition will persist when such social variables are controlled for. Along with standard anthropometric assessments, I plan to use several standard cognitive skill tests - visual motor integration, personal drawing, and perceptual tasks with abstract reasoning - selected for culture appropriateness and practicality for use by locally-trained staff under my supervision. Sociodemographic variables will be derived from a repeat of my 1968 village censuses, with added questions on interval social and economic changes, births and deaths. I anticipate this study of an unsual cohort of children should assist our general understanding of nutrition, infection, and behavior, as well as having direct implications for the problems of developing countries.